Plants in the genus Araucaria were abundant in the Mesozoic era, which began about 252 million years ago. The plants co-existed with dinosaurs. Today they are far less common than in the distant past. The trees that do exist are admired by many people, however. The monkey puzzle tree, the Bunya pine, and the Norfolk pine belong to the genus.
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| Cook pines on the Isle of Pines, New Caledonia Credit: NC21, CC BY 2.0 License |
New Caledonia
Many species of Araucaria live in New Caledonia, which is an archipelago in the southwest Pacific Ocean. It’s located about 750 miles east of Australia but is classified as a special collectivity of France. Captain James Cook from Britain is recognized as the first European to discover the archipelago.
James Cook was an officer in the Royal Navy and an explorer who travelled in the ship HMS Resolution. He discovered New Caledonia on his second voyage in the ship, which lasted from 1772 to 1775. He named the area after an old word for Scotland because some of the landscape features reminded him of that country. The name Cook pine is derived from the name of the explorer.
Features of the Tree
The Cook pine is not a true pine tree. It belongs to the order Pinales, like other conifers, and the family Araucariaceae. Pine trees belong to the family Pinaceae. The Cook pine is also known as the New Caledonia pine and the coral reef araucaria. The tree is able to grow in calcareous soil. On the Isle of Pines (part of the New Caledonia archipelago), it grows on top of coral reefs, which gives it one of its common names.
The tree is a popular ornamental plant beyond its native habitat and has some unusual features. It has a narrow, conical shape and in New Caledonia can grow as high as two hundred feet. Its branches are roughly horizontal and are arranged in whorls around its trunk. The triangular and overlapping leaves are tightly wrapped around the branches and are spiky. The grey trunk has a papery surface and sheds its bark in strips. The seed or female cones are oval or egg-shaped. They are larger than the elongated pollen or seed cones.
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| Credit: Forest and Kim Starr, CC BY 3.0 License |
The Leaning Trees
Though people had obviously notice the fact that many Cook pines lean before, a 2017 study discovered how widespread the growth habit was. The study was initiated by botanists at the California Polytechnic State University. Matt Ritter (one of the botanists) contacted a colleague in Australia and discovered that the trees there leaned in a different direction from those in California. This discovery stimulated further research.
With the help of other investigators, the California researchers obtained measurements from 256 trees on five continents. They not only found that the trees leaned but also discovered that their tilt was greater when they were further away from the equator.
Why and How Do the Trees Lean?
Scientists don’t know for certain why the trees lean. It may offer the advantage of the leaves meeting the sun’s rays at a more efficient angle. As in other plants, the trees produce food by photosynthesis. In this process light is absorbed by the leaves and used to make carbohydrates. If the trees do bend in order to absorb light better, the puzzle is why are they are apparently the only tree to develop this behaviour.
The mechanism of the lean is also a puzzle. The researchers speculate that it may have something to do with the way in which the wood responds to gravity and that it may involve a particular mutation or mutations.
Although the natural habitat of the tree is restricted, its population is currently not in any trouble. According to the IUCN (International Union for Conservation of Nature), it grows well in New Caledonia and is respected by the local people. I'm interested in seeing what scientists discover next about the biology of the intriguing Cook pine.
References
Araucaria columnaris data from The Gymnosperm Database
The strange Cook pine from New Scientist
Araucaria columnaris entry from the IUCN
